Pam De Almeida, who is mum to 18-month-old Sophia, was sat in a coffee shop experiencing "stares and whispers" from people around her.
"This is a pretty frequent occurrence for us you see, because my daughter Sophia was born with Down's syndrome," the mother wrote on a Facebook post, explaining what happened.
"Today it bothered me. It really bothered me."
But De Almeida was shocked when a stranger approached her and gave her and her daughter a completely unexpected reaction.
"The man greeted Sophia with a high five and a handshake, and Sophia smiled and waved back," De Almeida wrote.
"He looked at me with tears in his eyes and said: 'I have a story I would really like to share with you. But I am afraid I won't get through it without choking up.'
"I gently encouraged him to share, because now I was curious. This interaction was not what I was expecting."
The man told De Almeida he had watched a programme on the news the night before, where a woman had given birth to a child with a disability.
He explained that she was on TV defending her decision not to terminate her child, despite claiming doctors encouraged her to do so.
She continued: "He told me: 'The point is, you never know a person's impact on the world. You can never know what a person is able to do unless you give them a chance.'
"He looked at me just before he turned to walk away and said: 'You are a beautiful person. Your daughter is beautiful. Congratulations!'
"I immediately started to cry. There I sat in the middle of a coffee shop crying into a paper napkin.
"That man was the first complete stranger to ever congratulate me on the birth of my daughter Sophia. He was the first complete stranger to recognise her worth. Her value. Her beauty.
"In a world where my daughter’s life is whispered about, where she is stared at, this man saw her importance."
The heartwarming post, shared on De Almeida's blog's Facebook page 'Slice of Life', has been shared more than 12,000 times in just four days.
The post encouraged others to share their own joys of parenting a child with Down's syndrome.
"If only these people, could see the special joy these children have within them," one mother wrote.
"Life is way too short. My daughter is two with Down's syndrome and she makes me smile every damn day."
Another person commented on the post: "She is absolutely beautiful and I completely feel your pain. I wish I had met that man while out with my son, all I get is stares."
After reading the comments, De Almeida posted an update on Facebook.
"Sophia is so happy about all the amazing and supportive comments made," she said.
"It's totally making our week."